Aaqib Javed, the former Pakistan fast bowler and current bowling coach, has hit back at suspicions of foul play in Umar Gul's spectacular spell of reverse swing last week when his five-for demolished a frail New Zealand batting order at The Oval. The suspicions - that he got the ball to reverse earlier than usual - simply don't wash, says Aaqib, because reverse swing is an art that even Gul's team-mates have not perfected.

After the game, Daniel Vettori expressed some curiosity about how Gul managed to get reverse swing as early as the 12th over, and the matter was put to rest only after the match officials said there was no wrongdoing.

Aaqib - a superb practitioner of reverse swing in his playing days - was unimpressed. "If, as some people are indicating, they [Pakistan bowlers] are working on the ball, then why are the other guys in the team not getting the ball to reverse," he asked.

The reason, he said, is simple: reverse swing is an art requiring specific skills. "Why I say it is an art is because at the moment Gul is the only one from Pakistan who is able to do it," Aaqib told Cricinfo, before leaving for Nottingham, where Pakistan play the first semi-final of the World Twenty20 against South Africa.

The three most important requirements for reverse swing are a suitable action, speed (at least 85mph), and the perfect release. Gul, he says, has mastered all these - and also has the advantage of a slingy action, which makes his reverse swing unplayable. The sling was something Wasim Akram and Waqar Younis, who could reverse swing almost at will, also possessed.

"It is about releasing the ball at a particular angle," Aaqib said. "When you release the ball your wrists should point outside the off stump and you do that at higher speeds. If you bowl at 80mph then the batsman will easily guess that it is reverse. That's why people like Wasim, Waqar and now Gulli [Gul] get late, late swing due to their ability to bowl really fast."

Though Aaqib does not claim reverse swing will be the next big thing for bowlers in Twenty20, he reckons it is something close. "Only a few bowlers can get reverse swing. It is a very effective tool that separates the very best bowlers from the rest," he said.

No wonder Pakistan saved their best bowler for mostly the second half of the innings in all the four games of the tournament. In the first two, Gul bowled first change but in the last two games he has been their sixth bowler. Aaqib is not surprised at Younis' move to bowl Gul in the middle and death overs, where his reverse swing and lethal yorkers trouble the batsmen.

"Gul has matured in his art and he has got a great idea of bowling at the death or in the middle overs. He has become phenomenal," Aaqib said.

But Gul hasn't been the sole matchwinner with the ball for Pakistan. Aaqib said if South Africa have anything to be afraid of, it is Pakistan's versatile bowling attack. "We've a wonderful composition comprising new-ball bowlers, good middle-over and death specialists."

In fact, their slow bowling pair of Saeed Ajmal and Shahid Afridi has consistently confounded the opposition with their brilliant offspin-legspin combination before Gul's entry. Ajmal, the tournament's second highest-wicket taker, has managed to bounce back after concerns over his action while bowling the doosra.

"Our spinners are our advantage along with Gulli, who is always spot on." Aaqib said. He even said the Pakistan spin duo was at par with the best spinners in the tournament - the Sri Lankan pair of Muttiah Muralitharan and Ajantha Mendis.

Also, the return of Abdul Razzaq has beefed up Pakistan's new-ball attack after Sohail Tanvir's rusty performance in the earlier rounds.

Razzaq's experience helps him read the batsman, read the pitch and then bowl according to the situation. "From one end we have [Mohammad] Aamer, who has good pace, while Razzaq can be effective from the other."